Antibacterial potential of endophytic fungi from Neocarya macrophylla against ESBL-producing Gram-negative bacteria

The increasing prevalence of antibiotic resistance makes the search for novel antibiotics an urgent priority. This study focused on isolating, identifying, and screening endophytic fungi associated with Neocarya macrophylla for their antibacterial potential. Stem and leaf samples from healthy N. macrophylla plants were randomly collected from Jega, Kebbi state, Nigeria; surface-sterilized and then cultured to isolate fungal endophytes. The isolated fungi were identified via molecular techniques. The antimicrobial activity of the extracts obtained from the isolated endophytic fungi was evaluated using the spot on the lawn technique against extensively beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae. Seven fungal species were identified from the plant samples. Aspergillus species were most prevalent (71%) followed by Fusarium oxysporum and Alternaria alternata (14% each). Antibacterial assays against E. coli and K. pneumoniae revealed that A. niger isolate NMST_01 exhibited the highest antibacterial activity with inhibition zones of 10.7 ± 0.6 mm and 9 ± 1 mm against E. coli and K. pneumoniae, respectively. A. fumigatus strain NMST_02 and A. niger isolate NMST_03 also demonstrated moderate antibacterial activity. In contrast, A. pseudonomiae, Alternaria alternata, and A. nidulans exhibited no antibacterial activity. This study represents one of the first descriptions of the culturable endophytic fungi associated with N. macrophylla in Nigeria. The endophytes associated with N. macrophylla were predominantly Aspergillus sp. and they exhibited remarkable antibacterial activity against the tested organisms. Continued research on these endophytic fungi could lead to the discovery of valuable natural products with great pharmaceutical applications.